The goal of this research is to determine the mechanism of active transport of amino acids into mammalian cells. With this knowledge we hope to increase our understanding of important physiological cellular processes such as absorption and secretion as well as certain disease states brought about by defects in cellular transport. We are determining the number of kinds of transport systems for amino acids in varios mammalian cells such as Ehrlich ascites tumor cells, 3T3 and SV-40 virus-transformed cells and Chinese hamster ovary cells. In addition we are making membrane vesicle preparation for various cell lines to test the ability of these vesicles to bind or accumulate amino acids. Considerable effort is currently being spent attempting to solubilize and purify membrane proteins from vesicle preparations that retain the receptor site activity for certain amino acids. Non-ionic detergent treatment followed by centrifugation in sucrose gradients has been the most useful technique which results in the partial purification of leucine-binding activity from Ehrlich ascites cells. If we are successful in the purification of leucine-binding activity, we hope to attempt to reconstitute the system by adding the protein back to phospholipid vesicles. We are also studying the regulation of amino acid transport in various tissue culture cells. We have determined that the internal level of amino acids alters the membrane transport activity. High levels of alanine or glycine decrease their own transport activity and accumulated leucine transport. This regulation is being studied in both normal and malignant transformation. BIBLIOGRAPHIC REFERENCES: Cecchini, G., M. Lee, and D. L. Oxender. 1976. Transport of amino acid in intact 3T3 and SV3T3 cells. Binding activity for leucine in membrane preparations of Ehrlich ascites tumor cell. J. Supramolec. Struct. (in press). Oxender, D. L., G. Cecchini, M. Lee, and P. Moore. Amino acid transport and binding activity from membrane preparations of animal cells. To be presented at the FEBS-Symposium on the Biochemistry of Membrane Transport. Zurich, Switzerland, July 1976. Cecchini, G., M. Lee, P. Moore, and D. L. Oxender. Regulation of amino acid transport in mammalian cell culture. To be presented at ICN-UCLA conference on Supramolecular Structure (Text Truncated - Exceeds Capacity)